Smart photolithography

ABSTRACT

A photolithography method includes applying to a substrate a coating of a film forming composition containing a bonding resin and a film forming material and drying to form a film; selectively coating the film with a photosensitive composition including a photosensitizer to form a film pattern; exposing the film with the film pattern; and developing the film. Therefore, a film in a pattern and having excellent characteristics can be manufactured easily and efficiently. The photolithography method can be applied to any product which requires the formation of a film in a pattern.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to photolithography, and moreparticularly, to new photolithography used in forming film patterns, inwhich a mask is not required (named smart photolithography by theinventors of the prevent invention).

2. Description of the Related Art

Conventional methods for forming a film pattern include printing such assilk screen printing, photolithography and so on.

The printing method is mainly used in a plasma display panel (PDP) or afield emission display (FED), both being flat-panel display devices.However, according to this method, the thicknesses of the formedpatterns are not uniform. Also, it is difficult to form fine patterns.

According to a conventional photolithography, a desired thick-filmforming material is dispersed in a photoresist and a surfactant, adispersing agent and a co-photosensitizer are added thereto to form aphotoresist composition. The composition is applied as a coating on asubstrate and dried. Then, only a predetermined portion of the substrateis exposed using a photomask and developed, thereby completing a desiredfilm pattern. Such photolithography has the advantage that a finepattern can be formed, compared to the above-described printing method,but has the following disadvantages.

First, the manufacturing process is long and complicated.

Second, it is very difficult to control processing conditionsappropriately during exposure and developing processes. In detail, it isvery difficult to appropriately control exposure processing conditionssuch as exposure time, exposure illuminance or exposure temperature, anddevelopment process conditions such as pressure of a developingsolution. Since it is difficult to control the processing conditions towithin a desirable range, the pattern quality fluctuates depending onchanges in the exposure and development processing conditions.

Third, in the conventional exposure process, since exposure is performedfor an individual substrate using a batch-type exposure stand, theexposure process bottlenecks the overall photolithography process,thereby lowering the manufacturing efficiency.

Fourth, since exposure direction is fixed in one direction, that is, thesubstrate must be exposed from the front only, the film which isproduced always has uneven hardness. Thus, the pressure of thedeveloping solution should be carefully controlled during thedevelopment process.

Fifth, in the case of forming fine patterns, defects in mask patternssuch as deformation or blocked holes are frequently generated.

SUMMARY OF THE INVENTION

To solve the above problems, it is an objective of the present inventionto provide a photolithography by which a film pattern having improvedfilm characteristics can be manufactured easily and efficiently.

Accordingly, to achieve the above objective, there is provided a smartphotolithography method comprising the steps of:

(a) forming a film by coating a film forming composition having abonding resin and a film forming material on a substrate and drying theresultant;

(b) selectively coating a photosensitive composition comprising aphotosensitizer only on a predetermined portion of the film, accordingto a desired film pattern;

(c) exposing the resultant obtained in step (b); and

(d) forming a desired film pattern by developing the exposed resultantstructure.

In step (b), a coating method of the photosensitive composition is notspecifically restricted. Preferably, the photosensitive composition issprayed through a nozzle according to the desired film pattern.

In step (c), a photo-reaction is caused in the portion where thephotosensitive composition is coated without a photomask.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinbelow, smart photolithography according to the present inventionwill be described in detail.

First, a film forming composition including bonding a resin and a filmforming material is manufactured. Here, the film forming compositionincludes polyvinyl alcohol as its main component and may further includean additives such as dispersants and surfactants.

Separately from the photosensitive composition a photoresist,composition, comprising a photosensitizer, is manufactured, preferablyin a liquid phase. Such a photoresist composition basically includes aphotosensitizer or a photoresist and may further include an organicsolvent for adjusting viscosity, a polymer for adjusting viscosity, or asurfactant.

The photosensitizer is not specifically restricted, but sodiumdichromate aqueous solution, ammonium dichromate aqueous solution,4,4′-diazidostilbene-2,2′-sodium disulfonate (DAS) aqueous solution,2,5-bis(4′-azido-2′-sulfobenzyliden) cyclopentanon disodium salt (DAP)aqueous solution or stilbazolium polyvinyl alcohol aqueous solution isused. The concentration of the photosensitizer or photoresist aqueoussolution is preferably 0.01˜5.0% by weight.

The film forming composition is applied as a coating on the substrateand dried to form a film. Here, the coating method is not specificallyrestricted but a spin coating method or a sedimentation coating methodis preferably used.

As the substrate, a substrate for use in a vacuum fluorescent display(VFD), cathode ray tube (CRT), field emitting display (FED) or plasmadisplay panel (PDP) may be employed. However, the substrate is notrestricted to those used in display devices.

The photosensitive composition is selectively applied to on apredetermined portion of the dried film according to a desired filmpattern. Preferably, the desired film pattern is determined in advanceand the photosensitive composition is selectively sprayed only onto thepredetermined portion of the substrate through an ink jet nozzle.

The substrate onto which the photosensitive composition is selectivelyapplied is exposed to light from its inner surface, outer surface, orboth surfaces, that is, in any direction. During the exposure process, aphotomask is not necessary, unlike conventional photolithography. Also,instead of a conventional batch-type exposure stand, a tunnel-typeexposure stand is used as the exposure device, so that continuousexposure can be performed.

In the exposure process of the present invention, unlike conventionalphotolithography, since a photosensitive composition is selectivelyapplied on only a predetermined area of a film according to a desiredfilm pattern, the quality deviation depending on the temperature,duration and illuminance of exposure is greatly decreased. In otherwords, a long exposure time or high exposure illuminance does notadversely affect the film pattern size. Thus, the adhesion of a film toa substrate can be improved through sufficient exposure time andilluminance.

After performing the exposure process, a developing solution is sprayedonto the substrate with an appropriate pressure for development, therebycompleting a desired film pattern. During the development process, sincethe adhesion of the exposed film is very strong, the developmentpressure can be greatly increased, compared to the conventional process.Thus, it is easy to remove materials remaining on an undesired portion.

As described above, according to photolithography of the presentinvention, the tolerance in processing conditions can be greatlyenhanced during exposure or development.

Also, if photolithography according to the present invention is appliedto manufacturing a CRT, an exposure lens, which is an essential elementin a conventional exposure technique, is not necessary. In general, theexposure lens is very expensive and difficult to manufacture. Therefore,since the exposure lens is not necessary, the manufacturing cost isreduced, and the lead time for new product development is shortened.

The present invention has the following advantages.

First, fine patterning is obtained, within the fine patterningresolution of an ink jet nozzle and a motor for driving a printer head.

Second, the quality fluctuation depending on temperature, duration andilluminance of exposure can be reduced by selectively applying aphotosensitive composition comprising a photosensitizer only on apredetermined portion of a substrate. Also, film quality can be improvedthrough sufficient exposure time and illuminance.

Third, during exposure, since the substrate can be irradiated from anydirection, a tunnel-type exposure device can be used. Thus, continuousexposure is possible, which is suitable for mass production.

Fourth, since the adhesion of a formed film is very strong, the pressurewith which the developer is sprayed can be increased. Thus, in the caseof forming a fluorescent film, a residual color phenomenon whichfrequently occurs in the conventional art can be avoided.

Fifth, since a photomask is not necessary and an exposure lens and anexposure stand need not be specifically designed, the lead time fordeveloping new products can be noticeably reduced and the manufacturingcost can be significantly reduced.

The smart photolithography according to the present invention can beapplied to any product which requires the formation of a film pattern,for example, a VFD, a CRTa, FED, or, aPDP.

What is claimed is:
 1. A maskless photolithography method comprising:forming a film by applying a coating of a film-forming composition, thefilm-forming composition including a bonding resin and a film-formingmaterial, onto a substrate, and drying the coating to form a film;selectively applying a coating of a photosensitive composition,comprising a photosensitizer, to only a portion of the film to form afilm pattern; exposing the film on which the film pattern is disposed;and developing the film.
 2. The maskless photolithography methodaccording to claim 1, including spraying the photosensitive compositionthrough a nozzle onto the film to form the film pattern.
 3. The masklessphotolithography method according to claim 1, including exposing thefilm with the film pattern to light without a photomask.
 4. The masklessphotolithography method according to claim 1, including exposing thefilm, on which the film pattern is disposed, by irradiating at least oneof the surfaces of the substrate with light.
 5. The masklessphotolithography method according to claim 1, including exposing thefilm, on which the film pattern is disposed, by irradiating thesubstrate with light from more than one direction.
 6. The masklessphotolithography method according to claim 1, including exposing thefilm, on which the film pattern is disposed, by irradiating two oppositesurfaces of the substrate with light.